1-C Coastal Landscapes

Question 1

What are the characteristics of constructive waves?

Answer 1

The swash is stronger than backwash, so they build beaches. This is because the wave loses energy from the friction with the sand, and some water soaks into sand.

They are found in sheltered bays and spits, and are more common in summer.

Question 2

What are the characteristics of destructive waves?

Answer 2

The backwash is greater than the swash, so they comb beach material back into the sea.

The force from breaking destructive waves is sufficient enough to erode headlands. They are found in exposed bays. They are more common in winter.

Question 3

Describe the three processes of weathering

Answer 3

1. Mechanical - breakdown of rock without changing its chemical composition (e.g. salt weathering - salt crystals form inside the rock and expands and puts pressure on the rock)
2. Chemical - breakdown of rock by changing its chemical composition (e.g. carbonating weathering - carbonic acid in rain and seawater react with rocks that contain calcium carbonate and dissolve them)
3. Biological - breakdown of rocks by living things (e.g. plant roots break down rocks by growing into cracks on their surface and pushing them apart)

Question 4

What is mass movement and what are the three types of it?

Answer 4

Mass movement is the shifting of rocks and loose material down a slope. It causes coasts to retreat rapidly. If the material is full of water, it is more likely as it acts as a lubricant and makes the material heavier.

Three Types:

1. Slides - material shifts in a straight line
2. Slumps - material shifts with a rotation
3. Rockfalls - material breaks up and falls down slope

Question 5

Describe the four process of erosion

Answer 5

1. Hydraulic power - waves crash against rock and compress air in the cracks. This puts pressure on the rock and bits break off.
2. Abrasion - eroded particles in the water scrape and rub against rock, removing small pieces
3. Attrition - eroded particles in the water smash into each other and break into smaller fragments. They become rounded eventually.
4. Solution - dissolved carbon dioxide makes sea water acidic. The acid reacts with some rocks, which dissolves them.

Question 6

Describe the process of transportation of sediment on a coastal landscape

Answer 6

Longshore Drift

1. Waves follow the prevailing winds (eastwards)
2. The swash carries material up the beach in the same direction as the waves
3. The backwash then carries materials down perpendicular to the beach
4. Overtime, materials zigzags along the coast

Question 7

Describe the process of deposition

Answer 7

Deposition - when material carried by the seawater is dropped on the coast.

It occurs when the water does not have enough energy to carry the sediment. Therefore, low energy waves build up beaches - constructive waves.

Question 8

How does the geological structure of a coastline influence the formation of erosional landforms?

Answer 8

Discordant Coastline - alternating bands of hard and soft rock that are right angles to the coast. They form bays and headlands as the rocks erode at different rates

Concordant coastline - alternating bands of hard and soft rock that are parallel to the coast. Not many erosional landforms are made here

Rocks with lots of joints and faults erode faster.

Question 9

How are headlands and bays formed?

Answer 9

Formed on discordant coastlines -

1. Less resistant rocks are eroded quickly, which forms the bay (gentle slope)
2. More resistant rocks are eroded slowly, which forms the headland (steep slope)

Question 10

How are cliffs and wave cut platforms formed?

Answer 10

1. Waves erode mostly at the foot of a cliff. This forms a wave-cut notch, which is enlarged as erosion continues.
2. As the rock above the notch becomes unstable, it eventually collapses. The collapsed material is washed away and a new wave-cut notch is created.
3. Repeated collapsing results in cliffs retreating.
4. A wave-cut platform is the platform that is left bending as the cliff retreats

Question 11

How are caves formed?

Answer 11

Headlands often have cracks in them.
Through waves repeatedly crashing into them, mostly by abrasion and hydraulic power, the crack is enlarged and a wave forms.

Question 12

How are arches formed?

Answer 12

When the waves continue to erode the cave, it eventually deepens and breaks through. This is called an arch (e.g. Durdle Door in Dorset)

Question 13

How are stacks formed?

Answer 13

Erosion continues to wear away the rock, which supports the arch, until it eventually collapses. This forms a stack - an isolated rock that is separate from the headland (e.g. Old Harry in Dorset)

Question 14

How are beaches formed by deposition?

Answer 14

Beaches are found between the high water mark and the low water mark. They are formed by constructive waves depositing shingle and sand.

Question 15

How are spits formed by deposition?

Answer 15

1. Spits form at sharp bends in the coastline
2. Longshore drift transports sand and shingle past the bend and deposits it into the sea.
3. Strong winds and waves can curve the end (forming a recurved end)
4. The sheltered area behind the spit is protected from waves - plants accumulate here (it can become a mud flat or a salt marsh)

Question 16

How are bars formed?

Answer 16

1. A bar is formed when a spit joins two headlands together
2. The bar cuts off the bay between the headlands form the sea.
3. This means a lagoon can form behind the bar

Question 17

How are sand dunes formed?

Answer 17

1. They are formed when sand is moved up the beach by the wind
2. Obstacles (e.g. driftwood) cause wind speeds to decrease, so sand is deposited. This sand is colonies by plants and grasses, which stabilise the stand and encourages accumulation of sand. This forms an embryo dune.
3. Over time, the oldest dunes migrate inland.

Question 18

What are examples of deposition and erosion within a known coastline?

Answer 18

Dorset coast, near Swanage

Deposition:

• The Fleet Lagoon
• Chesil Beach
• the beach created in Swanage Bay

Erosion:

• Durlston Head is a headland
• Old Harry Stack is a stack
• Durdle Door is an arch

Question 19

What are the four different types of hard engineering?

Answer 19

Sea Wall, Gabions, Rock Armour and Groynes

Question 20

What are the benefits and costs of sea walls?

Answer 20

Sea Wall - a concrete wall that reflects waves back to sea

Benefits - it prevents erosion and acts as a barrier to prevent flooding

Costs - It creates a strong backwash, which erodes under the wall, and are expensive to build and maintain

Question 21

What are the benefits and costs of gabions?

Answer 21

Gabions - a wall of wire cages filled with rocks built at the foot of cliffs

Benefits - gabions absorb wave energy and reduce erosion. They are also cheap and easy to build

Costs - they are ugly and the wire cages corrode over time

Question 22

What are the benefits and costs of rock armour?

Answer 22

Rock Armour - boulders that are piled up along the coast

Benefits - they absorb wave energy and reduce erosion and flooding. They are also cheap.

Costs - Boulders can be moved around by strong waves, so need replacing

Question 23

What are the benefits and costs of groynes?

Answer 23

Groynes - wooden or stone fences that are built perpendicular to the coast to trap material transported by longshore drift

Benefits - they create wider beaches which slow the waves, which gives greater protection from flooding and erosion. Also, they are cheap

Costs - they starve beaches further down the coast of sand, making them narrower - making them more prone to flooding and erosion

Question 24

What are the two different types of soft engineering?

Answer 24

Beach Nourishment and Reprofiling, and Dune Regeneration

Question 25

What are the benefits and costs of beach nourishment and reprofiling?

Answer 25

Beach Nourishment and Reprofiling - sand and shingles from elsewhere or from lower down the beach is added to the upper parts

Benefits - it creates wider beaches, which slow the waves. This gives it greater protection from flooding and erosion

Costs - taking material from the seabed can kill organisms and it is very expensive

Question 26

What are the benefits and costs of dune regeneration?

Answer 26

Dune regeneration - creating or restoring sand dunes by either nourishment, or by planting vegetation to stabilise the sand

Benefits - sand dunes provide a barrier between land and sea, which absorbs wave energy. This prevents flooding and erosion. Also, stabilisation is cheap

Costs - The protection is limited to a small area and nourishment is very expensive.

Question 27

What is managed retreat or coastal realignment?

Answer 27

When people do nothing. It involves removing current defences and allowing the sea to flood the land behind. Over time, it will become marshland, which protects the land from flooding and erosion.

It is cheap and does not require maintaining, but it creates conflicts.

Question 28

Describe the reasons for coastal management within the areas of the Dorset coast

Answer 28

Areas within the Dorset coast are being erode, which puts properties and infrastructure at risk. Also, there is a danger to people from landslides and rockfalls.

Coastal management strategies have been used to prevent erosion.

Question 29

What are the coastal management schemes that they have used within the areas of the Dorset coast and what were the resulting effects and conflicts of them?

Answer 29

1. Groynes - new timber groins were put in along Swanage Bay in 2005-6. However, they stopped beach material moving down the coast and have starved areas of sand.
2. Sea Walls have been put in as protection.
3. Beach Replenishment - in winter 2005/2006, sand and shingle form the sea bed at Poole Harbour was added to the upper parts of Swanage beach. They have slowed the waves and have helped to protect cliffs and costal properties. However, they cost £5 million and will need to be repeated every 20 years